3 week old rescued kitten

I found a kitten in our old shed, on Sunday, I think its about 3 weeks old since its eyes are open and ears are up, its also walking now.

I can't really afford to bring it to the vet right now, it SEEMS fine, I got it KMR and feeding it at 3 hour intervals stimulating its butt before and after every feeding. it poops atleast once a day, and it seems to be playful... this is the first time I'm caring for a kitten this young, idk if what im doing is right? no shelters or rescuers near me so I can't give it anyone else..